1. Field of the Invention
This invention relates to video cameras having means for adjusting the color balance of the color video signals, and interchangeable lenses adapted to be used with such video camera.
2. Description of the Related Art
In the video camera or the like, the adjustment of the white balance of the color video signal has been made by setting forth the most standard spectral characteristic out of those of the commonly available photographic lenses, and on the basis of the color temperature information derived from the preset spectral characteristic and the nature of the light from an object to be photographed.
However, when the standard lens of the conventional video camera is interchanged by another one whose spectral characteristic is largely different from that of the standard lens, a problem arises that even for the same object, the white balance cannot be well adjusted.
To eliminate such a problem, there has already been proposed a technique that the information of the spectral characteristic of the interchangeable lens is memorized in, for example, a ROM or other suitable memory means positioned in the casing of the interchangeable lens, and, to adjust the white balance, is read out and transmitted to the camera body, in U.S. patent application Ser. No. 861,876 filed May 12, 1986, and assigned to the assignee of the present invention.
By the way, the image pickup system of the video camera is included with, for example, an IR cut filter or an optical low pass filter that functions to prevent formation of folded strain in the output of the image pickup element, and a color filter in front of the image pickup element. Such filters have no ideal spectral characteristics. For example, the IR cut filter blocks not only the infrared light component of the incident light but also a large fraction of the red color component. In actual practice, therefore, this fraction must be compensated for by modifying the spectral characteristic of the image pickup system of the video camera.